This invention relates to apparatus and method for determining the amount of gases (such as oxygen, nitrogen, carbon dioxide and carbon monoxide) dissolved in liquids (such as water or samples of blood). More particularly, this invention relates to apparatus which, unlike most conventional apparatus used for such determinations, does not employ liquid mercury, which is toxic and represents a health hazard.
A variety of apparatus for determining the amount of gases dissolved or entrapped in liquids is known to the art.
A device referred to as the Van Slyke apparatus for determining the amount of gases dissolved in liquids has been commercially available for many years. It employs a sample chamber, a shutoff valve, a mercury manometer and a mercury reservoir acting as a sealing fluid and as a means of producing vacuum.
U.S. Pat. No. 2,138,141 describes apparatus for determining the amount of gas contained in drilling mud used in drilling oil and gas wells. It employs a sample cylinder with a shutoff valve and piston and a Bourdon-type of pressure gauge protected by a metal diaphragm.
U.S. Pat. No. 2,680,060 describes a device embodying the features of the Van Slyke apparatus referred to above employing mercury as a sealing fluid and further employing a cylinder with a plunger to adjust the level of the mercury in the apparatus.
U.S. Pat. No. 3,171,722 describes a device resembling that of U.S. Pat. No. 2,680,060 above, used for injecting a gas sample into a gas chromatograph.
U.S. Pat. No. 4,315,890 relates to a sample tube for liquids having volatile components dissolved therein, and also having a reagent supported on an inert support such as glass wool in a portion of the sample tube, for indicating qualitatively by change in color whether certain volatile components, such as ethanol, are present in the sample liquid.
U.S. Pat. No. 4,607,342 describes a device for determining the quantity of carbon dioxide dissolved in carbonated beverages comprising a computer which controls solenoid-operated valves for admitting a sample of the beverage into a test chamber, stirring it to release carbon dioxide, measuring the pressure in the chamber, and automatically computing therefrom the level of carbonation of the beverage.
U.S. Pat. No. 4,745,794 describes functionally similar apparatus for determining the level of carbonation of beverages.
British Patent 2,190,196 describes apparatus for determining the quantity of gases dissolved in liquids comprising a conical flask having a side neck for a movable piston and a center neck for a pressure transducer.